<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      /* placehoder的属性  使用这种方式来实现 */
      * {
        margin: 0;
        padding: 0;
      }
      .box,
      body,
      html {
        height: 100%;
      }
      .box {
        display: flex;
        flex-direction: column;
      }
      header {
        height: 46px;
        width: 100%;
        background-color: pink;
      }
      footer {
        height: 50px;
        width: 100%;
        background-color: blue;
      }
      main {
        flex: 1;
        background-color: #ccc;
      }
    </style>
  </head>
  <body>
    <div class="box">
      <header></header>
      <main></main>
      <footer></footer>
    </div>
  </body>
</html>
